Control system.



F. H.` SHEPARD. CONTROL SYSTEM.' APPLicATloN m50 1uLY24, 1914.

1,236,774. Panmug. 14,1917;

PZ M2 asf/ag INVENTOR Franc/ls H. .Shepard ATTORNEY UNITED STATES PATENT oEEicE.

FRANCIS H. SHEPAILD, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO INESTINGHQU'SE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

coNTEoL SYSTEM.

To all whom t may concern.'

Be it known that I, FRANCIS H. SHEPARD,

a citizen of the United States, and a resident ofxNew Rochelle,- in the county of Westchester and State of New York, have invented a new and' useful- Improvement in Control Systems, of which the following is a specification.v

Myinvention relates to controlsystems for dynamo-electric machines, and it has special reference to the regulation of such polyphase induction motors as are einployed for propelling electric locomotives f Thus, automatic equalization of the load is or other electric vehicles. Oneof the objects of my invention is to provide a system for controlling ythe driving units or motors of an electric locomotive or train of electric vehicles in such manner that a predetermined division of the load between the driving units shall be maintained at all times, irrespective of variations in the electrical characteristics of the motors or in .the operation of the governing devices, or in the differences in diameters of the driving wheels.

More specifically, it is the obj ect of my invention to pro-vide automatic means for proportioning the totalvload between a plurality of motor-driven units which may constitute a plurality of separate motor-driven axles, a plurality of motor-driven trucks or a plurality of half units constitutmg an electric locomotive.

It has been customary in the past to provide means for equalizing the loads among a plurality of induction motor-driven units by rendering the operation of all of the motors but one, dependent upon the operation of the remaining motor, or by balancing the several motors against a manually controlled auxiliary' device, whereby the loads have been maintained substantially equal under all conditions of service.

According to my invention, however,` I

propose to accomplishthe desired results by employing aplurality of dii'erential relays which are severally associated with each of the driving units to be manipulated', and each of which is provided with auxiliary coils that are severally iniiuenced by the current traversing the respective motors.

obtained by mutually balancingeach of the vdriving units against the other.

Specification of Letters Patenth Application led :ilu-1y 24, 1914. Serial No. 852,799.

Patented Aug. 14, 1917.

For. the sake of simplicity, I shall set `forth my invention as embodying a pair of polyphase induction motors that are gov-v erned v by separate electrically controlled liquid rheostats, the system being of the multipleunit type.- In the case exemplified,`

the motors are associated, one with each truck of asingle locomotive, although .itl

is clear that a pair of motors for each truck may be balanced, or, that two half units ofa locomotive may be similarly adjusted.

In the accompanying drawing, Figure 1 is a diagrammatioview of a system of control embodying my invention, andFig/2 is a* view, in elevation, of an electric locomotive for the control of which my invention is adapted.

Referring to the drawing, a plurality ofl polyphase supply circuit conductors l, 2 and 3 are adapted to deliver energy, through a line switc LS, to the primarywinding P1 and P2 of a pair of polyphase induction motors M1 and M2 that are respectively provided with secondary windings S1 and S2 having connections to al plurality of liquid rheostats LRl and LR2, respectively.

"Ihe motor M1 is associated with a driving truck 5 of a locomotive 6 having another driving truck 7 which is propelled by motor M2, said trucks 5 and 7 having an articulated connectionI in the usual manner.

The liquid rheostats LRl and LR2 are of like construction and' each comprises a tank 10, a plurality of electrodes 11, an inlet opening 12, a centrally disposed stationary discharge tube 13, a regulating valve le, also oi tubular form vand adapted to be raised and lowered .within the member 13, and an electrically controlled pneumatic operating mechanism l5 for governing the actuation of the regulating valve 14:. Suitable means (not shown) is provided :tor effecting a continuous circulation of electrolyte through the rheostat tank 10, whereby the minimum level vof electrolyte is always maintained at a height corresponding to the upper end of ends of kthe electrodes 11v are partially immersed.. The excess of electrolyte is dis charged through the regulating valve 14 v comprises a cylinder 18. haying an of .the discharge tube 13, at which height the magnet valve associated with its upper end and adapted to control the admission of an operating fluid thereto, and an on magnet valve associated with its lower end and adapted to govern the'admission of operating fluid to the lower end of the cylinder. The cylinder is also provided with a Amovable piston 19 which is mechanically connected to the regulating valve Thus, the regulating valve 14 may be raised and lowered to X the level of the electrolyte,

' and, consequently, to regulate theamount of ,l tends to force it to its lowest point of travel.

It will be. understood, that, if the on magnet valve is also opened, balanced pressures acting upon thel opposite sides of the piston 19 will result, thereby holding said piston in whatever osition itV occupies, while, ifboth the o the on magnet valve are energized, pressure is released from above thev piston 19 .and admitted beneath it, whereby the unbalanced pressure relation effects an upward movement of said piston and `associated regulating valve 14. Foi` purposes of dis- I employ a plurality of diierential relays v. `DB1 and `DB2 that are respectively protinction, hereinafter the .oi magnet and the n magnet valves` associated with the rheostat LBl will be designated by employing the numeral 1 after their respective names, while the-corresponding valves asso-4 ciated with rheost'at LB2 will be followed by the numeral 2,1as on magnet-1.

In order to -provide for balancing lthe loads or torques between the several motors,

vided with movable switch members 24 and 25 which are respectively' adalip'tedtdmake.

and break the ener 'zing Icircuits. of-fo magnet-1 ando magnet-+2. The-difconstitute a. single member, anda plurality one to the other. DB2 similarly .embodies a plurality of cores" 6o ferential relay DB1 embodies a plurality of cores 26 and 27, whichmight vconveniently of energizin coils C1 and C2 which are` so disposed wit respect to the cores-26 and 27 and so connected as to act in opposition, the The differential relay 28 and 29 and coils C2 and Cl.

The coil C1 of relay DB1 and C l of relay DB2 are connected in series across a secondary winding 31 o f .a shunt transformer 32 having a primary' winding 33 magnet lvalve and that is energized from a secondary Winding 34 of a series transformer 35 having its primary winding 36 connected in series circuit with one of the conductors between motor M1 and the line switch LS. A series transformer 38 has its rimary windin 39 connected in series with a correspon ing conductor between the motor M2 and switch LS, and said transformer is provided with a' secondary winding 40' which serves to energize a windihg 41 of an auxiliary shunt transformer 42 having its secondary winding 43 connected to energize the coils C2 of relay DB1 and coil C2 of relay DB2 which are connected in series circuit.

The operation of the system is manually controlled by a master controller MC which embodies a movable conducting segment 45 and a plurality of stationary contact terminals B+, 46, 47 and 48 which are adapted for coperative engagement upon the positionindicating lines marked Lower, Hold and Baise Assuming the apparatus and circuit connections to be as shown, the operation of the system is as follows:

The master controller MC is first moved into its position marked 1i-aise, whereby a circuit is completed -froin the positive side of an auxiliary' battery B which includes terminal lB+,fsegment 45, terminal 46, energizing c oil 50 of line switch LS to the negative side of the battery B; another circuit is completed 'from thel terminal B+ which includes segment 45, terminal 47 and the energizing coils of on magnet-1 and f on magnet-2, in parallel relation, to the negative side'of the battery; While still another circuit'is established from .contact terminal B+, through segment 45, terminal 48, and thence through switch member 24 of relay DB1 andv energizing coil of off magnet`1 los to the battery and a multiple circuit through switch member 25 of relay DB2 and off `i ma eti-2 to the battery. e n

he energization `of coil 50 effects the` closure of the line switch LS, wherebyenergy is delivered from the supply circuit conductors 1, 2 and 3 through switch LS- and, thence, in parallel, to primary motor windings P1 and P2 of the respective motors M1 and M2. The motors are thus. started into operation.

Upon the com lation, of the circuits through the energizing coils of the various Y magnet valves. associated withv the respecnisms, said va ves "are actuated, whereby said pistons;v Under these conditions of un- Joalanced-pressure, the several pistons 19 and tive balancedressure operating mechatheir associated regulating valves 14 are l moved upwardly until .the movementv is aroperating fluid above the pistons 19, where.

rested, either by the operator or throuh 1 Ywithin the several rheostats LRl and. L 2

has been raised sufficiently, to bring themetors M1 and M2 to the desired speed, the

operator may move the master controller MC to its intermediate position marked Hold. In so doing, contact terminal 48 becomes disengaged from conducting segment 45 of the master controller MC and the energizing circuits through the ofi magnet- 1.and the olf magnet-2 are interrupted. The several 0E magnet valves, therefore, are permitted to open to admit by balanced-pressures act upon the pistons 19 which hold the regulating valves 14 at rest.

vmotor Ml should. for any reason whatsoever, have a tendency totake the larger portion of the load, or at least a portion greater than its intended amount, an excessive current traverses the pr1mary winding 36 of the series transformer 35, which, throughV the interposition of the auxiliary shunt' transformer 32, concurrently and similarly.

inuences the coil Cl of relay DB1 and Cl of relay DB2. Coil C1, therefore, predominates over coil C 2 of relay DB1 and coil "Cl overbalances coil C2 of relay DRQ.

Hence, relay Dltl is caused to raise its switch member 24 to'interrupt the energizing circuit of od magnet-1, while the energizing circuit of off magnet-2 is maintained intact The denergization of ed magnet-.1 permits said magnet valve to open to establish balanced pressure conditions within the cylinder 18, whereby further movement of the regulating valve lli of rheostat LRl is prevented.

lt is evident, therefore, that the operationof rheostat LR2 continues undisturbed while the operation of rheostat LRl is arrested. Rheostat LR2, therefore, serves to exclude more resistanceY from the secondary windings S2 of motor M2 causing said motor to increase its load until the desired division of total load is a ain obtained, when the opposing coils of lt e respective relays Dltl and DB2 neutralize each other and permit the closure of relay DB1, whereby od magnet--l is againenergized, and the upward movement of the regulating valve le and the electrolyte level of rheostat M1 until the desired equalization or division of load is secured.

The motors M1 and M2, therefore, are adapted to proportion the` load in accorda'nce with predetermined conditions and are mutually dependent, one on the other, for automatic adjustment thereof.

As already pointed out, the dierences in motor operation with respect to their tendency to carry load may be the result of differences in construction and electrical characteristics of the`motors themselves, or of the balanced pressure operating mechanisms A,which govern the liquid rheostats, or, perhaps, may be due to differences in densities of the electrolyte employed or in the rate fof its flow, although diderences in diameters ,iof driving wheels are, perhaps, the most g'common and troublesome. By means of my invention, therefore the mutual interdependence of the motors insures the proper division of load under all service conditions.

The particular means for controlling the operation of the several rheostats through.- vtheagency of the master controller forms lno part of my invention, except as it performs a necessary function in the operation of the system, and, therefore, no further detailed description thereof will be given, it being understood, of course, that, if the master controller MCbe moved to its position marked Lower, the several on magnet valves are also denergized, whereby vthe respective balanced-pressure operating mechanisms are moved downwardly to' lower the level of the electrolyte within the sevleral rheostats.

My invention, broadly considered, resides in the means for mutually balancing the `=load between a plurality of driving units, zwhether they be separate motors, motortion of said motor in accordance with relative current conditions of all of said motors throughout the nentire accelerating operation.

2. ln a control system, the combination with a plurality of electric motors adapted to drive a common load, of similar differential means energized in accordance with the current traversing each motor for rendering the operation of said motors mutually dependent throughout the entire accelerating operation..

3. In a control system, thecombination with aplurality of driving units, of mutual means including differential relays energized in accordance with the` current traversing each unit for proportioning the load between said units throughout the entire accelerating operation.

vand automatically controlling the of said rheostats.

4. In a control s stem, the combination witha plurality o electric driving units working on a common load, of means for governing the operation of said units, and diierential relays coperatin with each of said governing means for e ectin a division of the load in accordance wit mutual load conditions of said units.

5. The combination with a plurality of electrically propelled units for driving a common load, and means for separately governing the operation of said units, of similar means cooperating with each governin means and dependent upon predetermined current conditions of all of said units for effecting the operation of said governing vmeans throughout the entire accelerating operation. I

6. The combination with a plurality of electricallfyairopelled units for driving a common l and means for separately overning the operation of said units, of di erential relays severally associated with each of said governing means and adapted to be influenced by the loads of both of said drivg units for effecting a predetermined division of the load'between driving units.

7. The combination with a luralityl of driving unitspropelled by in uction motors, and a plurality of liquid rheostats for severally governing said driving units, of relays associated with each of said rheostats and each having a plurality of Acoils severally influenced by the currents of each of said driving units for mutually operation 8. The combination with a plurality of driving units propelled by electric motors, andelectro-pneumatic means for separately governing the operation thereof and severally embodying electrically operated valves for controlling the operation of said electropneumatic means, of a lurality of differential relays severally a a ted to control the action of said valvesan each having coils respectively connected to be influenced by the load currents of said 'driving units.

9. The combination 'with a plurality of electric driving units associated with a common load, means. for separately governin the operation of said units and a diiferentia relay associated with each of said governing means, of means responsive to current conditions associated ".vith each drivin unit and severally adapted to inuence t e action of both of said differential relays.

10. The combination with a plurality of drivin units propelled by electric motors and e ectro-pneumatically actuated liquidI rheostats for separately governin the operation thereofv and severa ly embo ying electrically operated valves for controlling the operation of said electro-pneumatically actuated rheostats, of a lurality of differential rela s severally a a ted to control the action o said valves, an a plurality of current transformers severall connected in circuit with the res ective e ectric motors and adapted to supp y energization to both of said differential relays under predetermined load 4conditions upon the respective electric motors.

In testimony whereof, I have hereunto llcribed my name this 9th day of July,

p l FRANCIS H. SHEPARD. Witnesses:

WM. H. Carni., C. WESLEY PoMnRY. 

